Money talks. That's why mobile phone advertising has become such an irresistible topic.

As mobile phone executives converge on the 3GSM World Congress in Barcelona, which runs from Monday to Thursday, many plan to meet and discuss how they can benefit from the rush toward ad-funded mobile services.

Interest in mobile ads is being fueled in part by higher-speed devices that are encouraging more users to surf the Web, by new broadcast mobile TV services that could attract a new breed of viewers on the go and, above all, by numerous ambitious startups, particularly MVNOs (mobile virtual network operators), which are eager to sink their teeth into a huge market. More than 2 billion handsets are spread across the globe, and their numbers are growing by the minute.

Arguably, the mobile phone is the most personal consumer goods device we own. It's a trusted communication companion, for the businessperson and consumer alike. And unlike a newspaper or even a computer, it's assigned to a single owner.

That has marketers licking their chops. They're excited over the prospect of being able to target their ads in a highly personalized way. And mobile operators, which have been reluctant to leverage their customer base for mobile marketing purposes, now see an opportunity to create a new revenue stream they simply can't resist.

Several groups are already testing the waters or are just about ready to dive in.

In Europe, for instance, HotSMS in the Netherlands currently delivers a free, ad-sponsored SMS (short message service) offer. Blyk in the U.K. and i-Wood in the Netherlands are preparing to launch free or heavily-subsidized voice and data services in exchange for mobile phone users' consent to receive ads.

Vodafone Group, Europe's largest mobile phone operator, is working separately with search engine giants Google and Yahoo. Google is developing a service that would link advertising to Internet searches -- a counterpart to its flagship business of selling ads linked to regular Internet searches.

With Yahoo, Vodafone aims to jointly develop advertisements in a variety of formats, including banner ads and short videos. To help make ads interesting to customers, the operator plans to offer discounts on services such as mobile TV, games and MMS (multimedia messaging service).

In the U.S., Sugar Mama, an MVNO owned by Virgin Mobile USA, gives prepaid customers additional minutes by watching online ads, answering questions by SMS or filling out surveys about products and services. Another MVNO startup, Xero Mobile plans to provide college students with subsidized talk time in return for viewing targeted, relevant advertising. AT&T, Sprint Nextel, and Verizon Wireless have signalled interest in developing mobile advertising strategies of their own.

Earlier this year, U.S. startup AdMob opened for business as a middleman for managing cell-phone ads. It joins Third Screen Media, which helps companies deliver ads to phones without a glitch.

Not surprisingly, in Japan, which is often far ahead of the curve in delivering new mobile phone services, NTT DoCoMo Inc. has been running small banner ads on its mobile portals for more than five years.

Clearly, there's money to be made. Informa Telecoms & Media, a division of Informa, expects mobile phone ad spending in 2007 to more than double from 2006 levels to $1.5 billion. By 2011, the market researcher projects spending of more than $11 billion.